As a handheld power tool, for example, an electric drill, is used for drilling a workpiece such as a plank, and a used work head is a drill bit; and for example, a screwdriver can be used for screwing or unscrewing a bolt, and the used work head is a screwdriver bit. A spindle of such type of handheld power tools is usually provided with a working chuck that is used for clamping a type of work heads required in clamping work, and such type of work heads can have different standards. When the work head needs to be replaced for other work, the original work head is required to be detached at first to be replaced with different work heads. This operation process of replacing the work heads is very troublesome.
At present, some drilling tools with double working chucks are emerged on the market, and can be selected or converted between the two types working chucks for use according to needs. In prior art, a tri-jaw type chuck is used to clamp the drill bit, this working chuck is made of metal and is complex in structure, and is thus large in weight; while the other working chuck is used to clamp a screwdriver bit, torque adjustment is required when the screwdriver bit executes the work of bolt screwing, generally the output end of a machine body close to an output shaft is provided with a mechanical control mechanism for realizing torque adjustment, when these functional parts complex in configuration and large in weight are applied to a gun-drill tool with the double working chucks, the gravity center of the whole machine is deviated to one side of the working chucks, and a horizontal distance still exists between the gravity center and a handle holding part, as a result, the wrist of an operator bears a torque in an execution operation process and fatigue is easily generated.
In addition, before the working chuck is subjected to position conversion, the matching between the working chuck and the output shaft or locking between the working chuck and a housing is required to be removed at first, in the prior art, the operator needs one hand to operate to remove the locking, generally, such a pressing action needs to be kept for such operation part till the position conversion of the working chuck is finished, for the tool whose position conversion of the working chuck needs to be carried out manually, the operator has to finish the conversion action with the hand that originally holds the handle, thus, the operator will frequently change hands for operation, the operation is very inconvenient, and such operation is unsafe for specific working occasions, for example, high altitude.